Technique for Aoi Event Monitoring

The present disclosure generally relates to event monitoring in a mobile communication system. The events relate to terminal devices being served in areas of interest. The technique presented herein can be implemented in the form of methods, computer program products, apparatuses and network systems.

Mobile communication systems can be divided into so-called areas of interest (AOIs). An AOI specifies a geographical portion within a mobile communication system. AOIs can be sub-divided into sub-areas to achieve a finer granularity. Such sub-areas can, for example be defined to include certain Tracking Areas (TAs), cells, and access nodes (ANs). An AOI can thus be represented by a list of TA identities (TAIs), a set of cell identifiers, certain AN identifiers and so on.

AOIs are flexible tools to implement location-based servicing of terminal devices. For example, the mobile communication system may be configured to provide communication services for certain terminal devices in certain AOIs only. As another example, content providers may offer location-based services for terminal devices being served in a certain AOI. In these examples, a notification is required when a terminal device moves into a certain AOI or leaves that AOI.

1 FIG.A Some mobile communication systems provide a subscription-based event notification mechanism that can also be used for configuring AOI notifications. In the following, one such notification mechanism will be described for an exemplary mobile communication system of the 5th Generation (5G) and with reference to the signalling diagram of.

1 FIG.A 1 FIG.A 110 120 130 140 120 110 110 120 130 140 The network entities involved in the signalling diagram ofcomprise an Application Function (AF)operated, for example, by a content provider. Moreover,illustrates several network entities of a core network domain of the mobile communication system: a network exposure function (NEF), a network repository function (NRF)as well as an access and mobility management function (AMF). The NEFacts as an entry point into the core network domain for the AF. The AFthus interacts with the core network domain through the NEF. The NRFis a centralized data repository in the core network domain. The AMFhandles access as well as mobility for terminal devices. It is configured to serve terminal devices within in a dedicated AOI or a dedicated sub-area thereof.

100 110 120 110 110 1 FIG.A In step S-of, the AFsends an event subscription request (here: an Nnef_EventExposure_Subscribe message) to the NEF. With this event subscription request, the AFsubscribes to be notified of a monitoring event of the type “AOI” for a dedicated terminal device “UE-X”. That is, the AFrequests to be notified when the terminal device “UE-X” enters (or leaves) the indicated geographical area.

110 120 120 110 110 In step S-, the NEFobtains one or multiple TAIS. To this end, the NEFtranslates the geographical area indicated by the AFinto TAIs. The resulting list of TAIs defines a dedicated AOI corresponding to the geographical area indicated by the AF.

120 135 140 120 140 120 110 130 130 130 140 130 140 140 140 In step S-, for each TAI indicated in the TAI list, sub-steps S-and S-are performed. In more detail, the NEFneeds to identify the one or more AMF(s)that serve the TAIs of the TAI list (i.e., that serve the AOI). To this end, the NEFperforms an NRF discovery procedure using as input each TAI obtained in step S-. The NRF discovery procedure includes sending, in step S-, an Nnrf_Nfdiscover request to the NRFand receiving, from the NRF, an NF discover response in step S-. The Nnrf_Nfdiscover request includes only a single TAI from the TAI list, in order for the NRFto provide the particular AMFserving the TA having this particular TAI (as the particular AMFmay also serve other TAs indicated in the TAI list). In the present example, the NF discover response returns a single AMF(here: “AMF1”) serving the TA with the particular TAI. This NRF discovery process is repeated for each TAI indicated in the TAI list.

150 120 140 110 100 120 110 In step S-, the NEFsubscribes to each AMF(here: “AMF1”) serving one or more TAIs as indicated in the TAI list. The subscription relates to the same event as that indicated by the AFin step S-. In more detail, the NEFsends an AOI event subscription message (here: an Namf_EventExposure_Subscribe message), indicating the AOI TAI list determined in step S-and the terminal device “UE-X” associated with the description.

1 FIG.A 140 160 140 150 140 In the exemplary signalling diagram of, it is assumed that the AMFis currently serving the terminal device “UE-X” (see step S-). In this case, the AOI event subscription procedure works properly as the AMFcan store information associated with the subscription message (see step S-) locally in context information maintained by the AMFfor the terminal device “UE-X”.

140 150 180 120 120 110 180 In the further signalling procedure, the AMFreturns, as a confirmation of the subscription message of step S-, an Namf_EventExposure_Subscribe response in step S-to the NEF. The NEFforwards this confirmation to the AFin step S-.

140 140 190 140 195 120 199 110 110 110 100 At this point, the AOI event subscription becomes applicable and the AMFtriggers AOI event monitoring. Since the terminal device “UE-X” is being served by the AMFin a TA within the AOI, the AOI event is detected in step S-. The AMFthus provides in step S-the requested AOI event notification in an Namf_EventExposure_Notify message to the NEF, which forwards this notification in step S-to the AF. The content of the notification, i.e., “AOI IN”, informs the AFthat the terminal device “UE-X” is served in the geographical area indicated by the AFin step S-.

1 FIG.A 1 FIG.A 1 FIG.B 140 140 150 It has been found that the notification procedure illustrated in the signalling diagram ofdoes not always work as expected. In particular, there may be malfunctions in case the terminal device is not being served by the AMFwhen the AMFreceives the Namf_EventExposure_Subscribe request (see step S-in). Such malfunctions will now be explained in greater detail with reference to the signalling diagram of.

200 250 100 150 160 260 140 140 250 140 140 120 270 140 140 140 250 1 FIG.B 1 FIG.A Steps S-to S-ofcorrespond to steps S-to S-as described above with reference to, respectively. In deviation from step S-, it is determined in step S-that the AMFcurrently does not serve the terminal device “UE-X” for which the AMFhas received an AOI event subscription message in step S-. This also means that the AMFpresently does not maintain a context for terminal device “UE-X”, which could be used as a “receptacle” for storing information associated with the AOI event subscription. As a consequence, the AMFreturns an error message to the NEFin step S-. This also means that the AOI event subscription does not become applicable and the event is not monitored by the AMF. In other words, the subscription will fail in the AMFif the AMFis not currently serving the terminal device “UE-X” when a corresponding AOI event subscription message is received in step S-.

140 110 120 100 200 150 250 140 To still make the AOI event subscription at the AMFapplicable to terminal device “UE-X”, the AFand the NEFcould repeatedly re-attempt to create the subscription, e.g., by periodically re-transmitting the messages in steps S-/S-und S-/S-up to a point in time when the AMFis actually serving the terminal device “UE-X”. Evidently, such an approach would not be a resource-efficient solution.

140 140 140 140 It has been found that similar problems as described above may occur even in cases in which the AOE event subscription is stored successfully by the AMFin context information maintained for a particular terminal device. In case the terminal device is deregistered from the AMF(e.g., because of an implicit “detach” due to an extended inactivity of the terminal device), the associated context information will however be deleted by the AMF. As a result, also the AOI event subscription will be lost. When the terminal device registers back at the AMF, the subscription no longer exists and the AOI event will be no longer monitored.

There is a need for a technique that avoids one more of the above or other drawbacks, and that enables an efficient event subscription procedure in an AOI context.

According to a first aspect, a method of triggering event monitoring for an event indicative of whether a terminal device is served in an AOI is presented. The method comprises the following steps performed by a network entity in a core network domain of a mobile communication system: detecting that the network entity is to serve a terminal device; registering as the serving network entity for the terminal device; receiving, in response to the registration, AOI event subscription control information relating to the terminal device; determining, based at least on the AOI event subscription control information, if an AOI event subscription shall be applied to the terminal device; and triggering AOI event monitoring for the terminal device if the AOI event subscription shall be applied to the terminal device.

The AOI event subscription control information may indicate, for each of one or more network entities, one or more sub-areas of the AOI associated with the respective network entity (e.g., served by the respective network entity). In such a case, determining if the AOI event subscription shall be applied to the terminal device may comprise determining if the AOI event subscription control information indicates the serving network entity in association with (e.g., mapped to) a sub-area in which the terminal device is served by the serving network entity.

Determining if the AOI event subscription shall be applied to the terminal device may in some variants comprise determining if the serving network entity has received an AOI event subscription message indicative of the served sub-area. The AOI event subscription message may be indicative of a conditional subscription that can become applicable dependent on a content of the AOI event subscription control information. The method may comprise receiving the AOI event subscription message. This message may be indicative of one or more sub-areas for which the AOI event subscription can (e.g., conditionally) apply. The AOI event subscription message may not yet be indicative of any particular terminal device (e.g., for which the subscription shall apply). The AOI event subscription may not become applicable until a particular terminal device has been identified to which it shall be applied (and possibly one or more further conditions are met). In some variants, the AOI event subscription shall selectively be applied to terminal devices that are served by the network entity in one of the one or more sub-areas indicated in the AOI event subscription message. The AOI event subscription message may be received prior to the step of registering as the serving network entity.

The AOI event subscription message may be received from an NEF of a 5th Generation-, 5G-, enabled core network domain, in particular in an Namf_EventExposure_Subscribe message, or from a service capability exposure function gateway (SCEF) of a 4th Generation-, 4G-, enabled core network domain. The method may be performed by an AMF of a 5G-enabled core network domain or a Mobility Management Entity (MME) of a 4G-enabled core network domain.

Registering as the serving network entity may comprise sending a registration message. The registration message may be sent (i) to one of a UDR and a UDM of a 5G-enabled core network domain or (ii) to one of a UDR and a home subscriber server (HSS) of a 4G-enabled core network domain. The method may comprise receiving subscriber data for the terminal device in response to the registration message. The AOI event subscription control information may be received together with or as part of the subscriber data.

The AOI may include one or more sub-areas. Each sub-area may be associated with (e.g., map to) at least one of a dedicated TAI, a dedicated cell identifier, a dedicated access node identifier and a dedicated tracking area code (TAC).

In some implementations, AOI notification event monitoring comprises determining that the terminal device has entered or left the AOI, and sending a corresponding AOI event notification (e.g., “AOI IN” or “AOI OUT”) towards a server in a content provider domain. The AOI event notification may also be indicative of the associated terminal device.

A second aspect is directed at a method of handling an event subscription request directed at an event notification dependent on whether a terminal device is served in an AOI, wherein the AOI includes one or more sub-areas. The method comprises the following steps performed in a core network domain of a mobile communication system: receiving an AOI event subscription request indicating a terminal device and an AOI for which an AOI event subscription is requested; determining one or more core network entities serving one or more sub-areas included in the AOI; determining AOI event subscription control information indicating, for each of the one or more serving network entities, one or more sub-areas of the AOI associated with the respective network entity; and triggering an association between the AOI event subscription control information and the terminal device indicated in the AOI event subscription request in a core network database storing subscriber data for the terminal device.

The method of the second aspect may comprise conditionally subscribing to the one or more core network entities to provide an AOI event notification for the one or more sub-areas. Conditionally subscribing to the one or more network entities to provide the AOI event notification may comprise sending, to the one or more core network entities, an AOI event subscription message indicative of one or more of the sub-areas for which an AOI event subscription is to be conditionally applied by the respective network entity. The AOI event subscription message may not be indicative of any particular terminal device (e.g., for which the subscription shall apply). As such, the AOI event subscription may not apply until a particular terminal device has been identified for which the AOI event subscription shall apply. The AOI event subscription shall in some variants selectively be applied to terminal devices that are served by the network entity in one of the one or more sub-areas indicated in the AOI event subscription message.

The AOI event subscription request may be received from a server located in a content provider domain. The method of the second aspect may comprise receiving an AOI event notification indicative of the terminal device having entered or left the AOI. The method may further comprise notifying the server about a content of the AOI event notification (e.g., “AOI IN” or “AOI OUT”).

Triggering the association may comprise sending an information message indicative of the terminal device and the AOI event subscription control information towards the core network database. The message may be sent (i) to one of a UDR and a UDM of a 5G-enabled core network domain or (ii) to one of a UDR and an HSS of a 4G-enabled core network domain.

The method of the second aspect may be performed by an NEF of a 5G-enabled core network domain or an SCEF of a 4G-enabled core network domain.

According to a third aspect, a method of providing event subscription control information for enabling an event notification dependent on whether a terminal device is served in an AOI is presented, wherein the AOI includes one or more sub-areas. The method comprises the following steps performed in a core network domain of a mobile communication system: receiving, for the terminal device, AOI event subscription control information indicating, for each of one or more network entities, one or more sub-areas of the AOI associated with the respective network entity; storing the AOI event subscription control information in a subscriber context of the terminal device; receiving a request for subscriber data relating to the terminal device; and providing, in response to the request for subscriber data, the AOI event subscription control information together with or as part of the subscriber data.

In the method of the third aspect, the AOI event subscription control information may be received from an NEF of a 5G-enabled core network domain or an SCEF of a 4G-enabled core network domain. The method may be performed by a UDR of a 5G-enabled or of a 4G-enabled core network domain.

A fourth aspect is directed at a method of providing event subscription control information for enabling an event notification dependent on whether a terminal device is served in an AOI, wherein the AOI includes one or more sub-areas. The method comprises the following steps performed in a core network domain of a mobile communication system: receiving, for the terminal device, a registration request from a core network entity serving the terminal device; sending, in response to the registration request, a request for subscriber data relating to the terminal device; receiving, in response to the request for subscriber data, the requested subscriber data together with or including AOI event subscription control information indicating, for each of one or more network entities, one or more sub-areas of the AOI associated with the respective network entity; and providing, in response to the registration request, the AOI event subscription control information, or information derived therefrom, to the serving core network entity.

In the method of the fourth aspect, the AOI event subscription control information may be received from a UDR of a 5G-enabled or of a 4G-enabled core network domain. The method may be performed by a UDM of a 5G-enabled core network domain or an HSS of a 4G-enabled core network domain.

Also provided is a computer program product comprising program code configured to implement the steps of any of the preceding claims when the computer program product is executed on a processor. The computer program product may be stored on a computer-readable recording medium.

In a fifth aspect, an apparatus is provided for triggering event monitoring for an event indicative of whether a terminal device is served in an AOI. The apparatus is configured to be comprised by a network entity in a core network domain of a mobile communication system and is adapted to: detect that the network entity is to serve a terminal device; register as the serving network entity for the terminal device; receive, in response to the registration, AOI event subscription control information relating to the terminal device; determine, based at least on the AOI event subscription control information, if an AOI event subscription shall be applied to the terminal device; and trigger AOI event monitoring for the terminal device if the AOI event subscription shall be applied to the terminal device.

The apparatus of the fifth aspect may be adapted to perform the method of the first aspect.

In a sixth aspect, an apparatus is provided for handling an event subscription request directed at an event notification dependent on whether a terminal device is served in an AOI, wherein the AOI includes one or more sub-area. The apparatus is configured to be comprised in a core network domain of a mobile communication system and is adapted to: receive an AOI event subscription request indicating a terminal device and an AOI for which an AOI event subscription is requested; determine one or more core network entities serving one or more sub-areas included in the AOI; determine AOI event subscription control information indicating, for each of the one or more serving network entities, the one or more sub-areas of the AOI associated with the respective network entity; and trigger an association between the AOI event subscription control information and the terminal device indicated in the AOI event subscription request in a core network database storing subscriber data for the terminal device.

The apparatus of the sixth aspect may be adapted to perform the method of the second aspect.

In a seventh aspect, an apparatus is provided for providing event subscription control information for enabling an event notification dependent on whether a terminal device is served in an AOI, wherein the AOI includes one or more sub-areas. The apparatus is configured to be comprised in a core network domain of a mobile communication system and is adapted to: receive, for the terminal device, AOI event subscription control information indicating, for each of one or more network entities, one or more sub-areas of the AOI associated with the respective network entity; store the AOI event subscription control information in a subscriber context of the terminal device; receive a request for subscriber data relating to the terminal device; and provide, in response to the request for subscriber data, the AOI event subscription control information together with or as part of the subscriber data.

The apparatus of the seventh aspect may be adapted to perform the method of the third aspect.

In an eight aspect, an apparatus is provided for providing event subscription control information for enabling an event notification dependent on whether a terminal device is served in an AOI, wherein the AOI includes one or more sub-areas. The apparatus is configured to be comprised in a core network domain of a mobile communication system and is adapted to: receive, for the terminal device, a registration request from a core network entity serving the terminal device; send, in response to the registration request, a request for subscriber data relating to the terminal device; receive, in response to the request for subscriber data, the requested subscriber data together with or including AOI event subscription control information indicating, for each of one or more network entities, one or more sub-areas of the AOI associated with the respective network entity; and provide, in response to the registration request, the AOI event subscription control information, or information derived therefrom, to the serving core network entity.

The apparatus of the eighth aspect may be adapted to perform the method of the fourth aspect.

Also provided is network system comprising two or more of the event monitoring triggering apparatus of the fifth aspect; the event subscription request handling apparatus of the sixth aspect; the control information providing apparatus of the seventh aspect; and the control information providing apparatus of the eighth aspect.

In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent to one skilled in the art that the present disclosure may be practiced in other embodiments that depart from these specific details.

While, for example, the following description focuses on an exemplary core network configuration in accordance with 5G specifications, the present disclosure is not limited in this regard. The present disclosure could, for example, also be implemented in other mobile communication systems having a core network domain complying with 4G specifications or beyond-5G specifications.

Those skilled in the art will further appreciate that the steps, services and functions explained herein may be implemented using individual hardware circuits, using software functioning in conjunction with a programmed processor or general purpose computer, using one or more application specific integrated circuits (ASICs) and/or using one or more digital signal processors (DSP). It will also be appreciated that when the present disclosure is described in terms of a method, it may also be embodied in one or more processors and one or more memories coupled to the one or more processors, wherein the one or more memories store one or more computer programs that control the one or more processors to perform the steps, services and functions disclosed herein when executed by one or more processors.

In the following description of exemplary realizations of the present disclosure, the same reference numerals denote the same or similar components.

2 FIG. 100 100 illustrates an embodiment of a mobile communication systemin which the present disclosure can be realized. The mobile communication systemmay be configured as a subscription-based cellular communication network operated by a mobile network operator (MNO).

2 FIG. 100 100 As shown in, the mobile communication systemcomprises a content provider domain (CPD) configured to provide digital content to a subscriber domain (SD). The systemfurther comprises a core network domain (CND) and an access network domain (AND) functionally arranged between the CPD and the SD. In some variants, at least the CND and the AND are split into a user plane for transporting application traffic (e.g., digital content) and a control plane for transporting control signalling. As understood herein, a particular domain comprises one or more devices, nodes or functions under control of a particular domain owner, such as a subscriber, an MNO or a content provider.

200 The CND and the AND each comprises one or more network entities, such as network nodes or network functions (NFs). For example, the AND may comprise one or more access points or base stations (not shown) configured to establish one or more wireless communication links to the SD. The CND comprises one or more core network entities, such as one or more AMFs, an NEF, an UDR, an UDM, and others.

150 150 The SD comprises one or more terminal devicesconfigured to wirelessly communicate with the AND under a subscription regime. Exemplary terminal devicescomprise a user equipment-(UE-) type device (e.g., a smartphone, tablet or television set) or an Internet of Things-(IoT-) type device (e.g., a car or a wearable device such as a head-, hand-or body-mounted device) with wireless communication capabilities towards the AND.

2 FIG. 1 1 FIGS.A andB 100 110 110 110 150 With continued reference to, the systemfurther comprises a content server(e.g., an Internet-based server offering, for example, media download or media streaming services). The content serveris located in the CPD and may, e.g., in a 5G scenario, implement the AF of. The content serveris in some variants configured to provide location-based services to the one or more terminal devicesin the SD. Such location-based services may be limited to a certain geographical area.

200 200 202 204 202 204 202 202 200 206 208 2 FIG. 3 FIG. 3 FIG. Exemplary realizations of the core network entitiesillustrated inwill now be explained with reference to. As illustrated in, in one exemplary hardware implementation, each of the entitiescomprises a processorand a memorycoupled to the processor. The memorystores program code that controls operation of the processorto implement one or more aspects of the present disclosure. As understood herein, the processormay be realized using any processing circuitry and is not limited to, for example, a single, localized processing core but may, for example, also have a distributed (e.g., cloud-based) topology. Each of the entitiesfurther comprises an optional input interfaceand an optional output interfacefor communication with other entities in the CND or outside the CND.

4 4 FIGS.A toD 5 5 FIGS.A andB In the following description, an exemplary 5G realization implementing aspects of the present disclosure will be described with reference to the flow diagrams ofand the signalling diagrams of, and it will be apparent to one skilled in the art that similar signalling realizations will apply in case of a 4G or a combined 4G/5G implementation.

1 1 FIGS.A andB 5 5 FIGS.A andB 160 170 170 170 160 170 160 170 Compared to the signalling diagrams of, the signalling diagrams offurther illustrate a UDRand a UDM. The UDMcentrally handles data (in particular subscriber data) in the CND. To this end, the UDMhosts or has access to the UDRthat, in turn, hosts a subscriber database. The UDMitself may store session context information for later retrieval when a session is created. Some NFs may access the UDRdirectly and some only via the UDM.

130 130 130 130 130 3GPP TS 23.501 V 15.4.0 (2018-12) and later defines architectural aspects of a 5G service based architecture (SBA). According to this SBA, NFs use service-based interactions to consume services from other NFs. The discovery of services and of NFs producing them is provided by the NRF. Service producing NFs register, update or deregister their profiles in the NRF. Service consuming NFs discover services offered by NF producer instances by querying the NRFabout NF instances offering services of a given type. NFs may subscribe and unsubscribe to changes in the status of NFs registered in the NRF. Based on such subscriptions, the NRFor other NFs may notify subscriber NFs of local status changes. This subscription framework is utilized in the context of the following embodiments for triggering AOI event notifications.

120 130 150 130 150 150 150 150 150 1 1 FIGS.A andB Presently there are three types of the AOI event subscriptions from the NEFto the AMF(see), either the subscription applies to “any terminal device” (that is, any terminal devicethat happens to be located in an AOI served by the AMF), a group of terminal devices, or one single terminal device. Details in this regard can be gathered from 3GPP TS 29.522 V 17.5.0 (identification of an individual terminal devicevia the “gpsi” attribute; identification of a group of terminal device(s)via the “exterGroupId” attribute; identification of any terminal devicevia the “anyUeInd” attribute) and 3GPP TS 29.503 V17.6.0 (see the UDM services indicated in sections 5.5.2.2.2 and 6.4.3.2.2). See also 3GPP TS 29.122 V17.5.0. In the context of the following embodiments, a fourth AOI event subscription type is presented, which is also called “specific UE” herein.

150 140 110 170 160 140 150 1 1 FIGS.A andB 4 4 5 5 FIGS.A toD,A andB In case the subscription applies to one individual terminal device, and if the AMFcurrently does not hold the terminal device context, then the subscription will fail (as has been explained with reference toabove). To avoid such a failure, in the embodiments illustrated in, the NEFstores further subscriber data (possibly via the UDM) in the UDR. The further subscriber data are referred to as AOI subscription control information herein and may be evaluated by the AMFin the context of the AOI event subscription type “specific UE” to determine if the AOI event subscription shall be applied to a particular terminal device.

4 4 5 5 FIGS.A toD,A andB 110 140 150 150 140 140 150 In the embodiments illustrated in, the NEFis configured to send an AOI event subscription message for the AOI event subscription type “specific UE” to AMF. The AOI event subscription type “specific UE” allows this subscription to be stored successfully in the AMF context (and not per terminal device). This can also be seen as a conditional subscription. When a certain terminal deviceis to be served by the AMF, the AMFobtains the AOI subscription control information (in a registration response), and then determines whether the subscription shall apply (“unconditionally”) for this terminal device.

140 150 140 150 170 As such, a new type of a subscription to the AMFis proposed in this exemplary embodiment, that applies to certain terminal devices(“specific terminal device”). The AMFobtains knowledge for which terminal devicesthe subscription shall apply based on the AOI event subscription control information as obtained during registration to the UDM.

140 150 140 As such, only one subscription request is required per AMF, rather than managing a subscription per terminal device. The AMFthen takes control (based on the AOI event subscription control information) as to whether and when a subscription shall apply.

4 5 FIGS.A andA 120 110 402 502 110 Referring now to, the procedure starts with the NEFreceiving an AOI event subscription request from the AF(“Nnef_EventExposure_Subscribe request”) in steps S-and S-. This request indicates a particular terminal device (“UE-X”) and a particular AOI (defined by a geographical area “GeoArea” in this example, such as a certain city or a part thereof) for which an AOI event notification is requested. The AFmay use such AOI event notifications to provide a location-based service to the terminal device UE-X.

404 120 140 140 120 504 120 140 506 140 508 510 120 508 130 510 130 4 FIG.A 5 FIG.A 5 FIG.A 5 FIG.A In step S-of, the NEFdetermines one or more core network entities (i.e., AMFs) serving one or more sub-areas included in the AOI (each sub-area may be served by one or more AMFs). To this end, the NEFfirst translates the AOI into one or multiple TAIs, as illustrated by step S-of. In this way, a list of TAIs is obtained that correspond to the AOI. In a second step, the NEFidentifies the one or more AMFsserving the TA associated with these TAIs by looking up for each TAI in the TAI list (step S-in) the AMFserving this TA (steps S-and S-in). In more detail, the NEFin step S-sends a Nnrf_Nfdiscover request for a given TAI (with the NF indication “AMF”) to the NRFand receives, in step-S-, an NF discover response from the NRF.

5 FIG.A 130 508 140 1 140 2 140 140 404 508 510 120 406 140 140 140 In the example of, it is assumed that the TA corresponding to the TAI signalled to the NRFin step S-is served by two AMFs-,-. In other variants, only one AMFmay serve a given TA. Each AMFmay in principle be related to one or multiple TAIs from the TAI list. From the result obtained in steps S-and S-/S-, the NEFdetermines, in step S-, AOI subscription control information indicating, for each of one or more AMFs, one or more sub-areas of the AOI (in terms of TAIS) served by and, thus associated with, the respective AMF. As an example, the AOI subscription control information can take the form of a mapping of the AOI TAIs to one or multiple AMFs. In the mapping, for each AMFone of multiple TAIs served by this AMF may be indicated. Of course, the AOI subscription control information may also have other formats or contents.

408 120 402 502 150 150 120 160 512 140 140 170 3 3 120 160 140 120 160 170 514 160 512 514 5 FIG.A Then, in step S-, the NEFtriggers an association between the AOI subscription control information and the terminal device “UE-X” indicated in the AOI event subscription request received in step S-/S-. The association is triggered in the UDR, i.e., in a core network database storing subscriber data for the terminal device “UE-X” (and other terminal devices). In more detail, the NEFsends an Nudr_DataRepository_Create request to the UDR(see step S-in) to trigger storage of the AOI subscription control information for this terminal device (and to indicate that for this terminal device an AOI event notification is requested). The AOI subscription control information defines an event applicability, i.e., for which AMFs(and TAIs) the AOI event subscription applies. The AOI subscription control information will be read by an AMFat registration to the UDM(Nudm_UECM_Registration), as will be explained below. For this reason, the proposed procedure fits under the AmfgppAccessRegistration scheme (seeGPP TS 29.503 V. 17.6.0, clause 5.3.2.2.2). The NEFtherefore is configured to store information in the UDRthat is expected to be read by an AMF. As an alternative, the NEFmay store the AOI subscription control information in the UDRvia the UDM. In step S-, the UDRconfirms the request of step S-via a S-Nudr_DataRepository_Create response.

410 160 120 512 412 160 120 408 4 FIG.B 5 FIG.A 4 FIG.A Referring now to step S-of, the UDRthus receives the AOI subscription control information from the NEFvia the Nudr_DataRepository_Create request (see also step S-in). In step S-, the UDRstores the AOI subscription control information in a subscriber context of the terminal device “UE-X” (e.g., as part of the associated subscriber information or linked thereto). This storing of the AOI notification information has been triggered by the NEFin step S-of.

5 FIG.A 120 516 522 140 1 140 2 506 510 140 1 140 2 140 1 140 2 140 Returning now to, the NEFsends in steps S-and S-an AOI event subscription message (i.e., an Namf_EventExposure_Subscribe request) to each of the AMFs-,-“discovered” in steps S-to S-. These messages include configuration information to configure the AMFs-,-. The configuration information includes a “specific UE” flag (or a similar indicator) and the AOI TAIS for which the respective AMF-,-is to be configured to provide AOI event notifications on a subscription basis (note that an AMFmay serve a plurality of TAs, and not TAs all may be part of the AOI).

140 1 140 2 516 522 150 140 1 140 2 140 1 140 2 538 The “specific UE” flag configures the respective AMF-and-to process the AOI TAIs received in steps S-and S-when having to determine if an AOI event subscription shall be applied to a specific terminal devicethat is to be served by the respective AMF-and-(as will be explained in greater detail below). In some variants, the “specific UE” flag may configure the respective AMF-and-to store the associated TAIs in a certain subscription type context for later retrieval (see discussion of step S-below).

150 150 160 512 408 410 4 FIG.A 4 FIG.B It is to be noted that a particular terminal device(such as “UE-X”) is not indicated in the configuration information since a resulting AOI event subscription shall only apply to “specific” terminal devicesbased on the AOI event subscription control information stored in the UDRin step S-(see also step S-inand step S-in).

518 524 140 1 140 2 120 120 520 526 528 110 140 140 110 502 5 FIG.A In steps S-and S-, the respective AMF-,-stores the configuration information as part of its AMF context information, and then confirms this in an Namf_EventExposure_Subscribe response to the NEF. The NEF, upon receipt of the Namf_EventExposure_Subscribe responses in steps S-and S-, sends an Nnef_EventExposure_Subscribe response in step S-to the AF. While two AMFsare involved in the signalling diagram of, more or less AMFsmay be involved in other scenarios, also depending on the size of the particular AOI signalled by the AFin step S-.

4 4 5 FIGS.C,D andB 5 FIG.A 4 FIG.C 5 FIG.B 4 FIG.C 5 FIG.B 4 FIG.D 110 502 140 2 140 2 420 528 140 2 170 422 530 170 430 Referring now to, it is assumed that at some point, the terminal device “UE-X” (as indicated by the AFin step S-of) moves into a TA served by the AMF-, so that the AMF-detects that it is to serve that terminal device (step S-inand step S-in). The AMF-will thus register itself as the serving AMF for the terminal device “UE-X” to the UDM(step S-in). To this end, it sends in step S-ofan Nudm_UECM_Registration request indicative of terminal device “UE-X” to the UDM(see step S-in).

170 432 160 532 414 160 534 416 140 2 170 434 170 140 2 436 536 140 2 424 4 FIG.D 5 FIG.B 4 FIG.B 5 FIG.B 4 FIG.B 4 FIG.D 4 FIG.D 5 FIG.B 4 FIG.C In response to the registration request the UDM, in step S-of, sends to the UDRa request for subscriber data relating to the terminal device “UE-X” (see step S-in: Nudr_DataRepository_query request, and step S-in). The UDRresponds to this request with a Nudr_DataRepository_query response (see step S-inand step S-of) that provides the AOI event subscription control information (i.e., the AOI event applicability) together with or as part of the subscriber data. Moreover, the response further includes an optional new indication, or flag, “AOI for this specific UE”, which triggers a dedicated behaviour of the AMF-. This information is received by the UDMin step S-of, provided by the UDMto the AMF-in step S-of(see Nudm_UECM_Registration response in step S-of) and received by the AMF-in step S-of.

140 2 536 140 2 538 538 425 524 140 2 425 426 5 FIG.B 5 FIG.B 4 FIG.C 5 FIG.A 4 FIG.C 4 FIG.C When the AMF-detects the flag “AOI for this specific UE” in the subscriber data received in step S-, or responsive to the received AOI event subscription control information in case no such flag is implemented, the AMF-performs the checks indicated in step S-ofto determine if an AOI event subscription shall be applied to the terminal device “UE-X”. This determination is generally based at least on the AOI event subscription control information received in step S-of(see also step S-in) and, in the present realization, also on the configuration information received earlier in step S-of. The AMF-triggers AOI event monitoring for the terminal device “UE-X” if it is determined in step S-ofthat the AOI event subscription shall be applied to the terminal device “UE-X” (see step S-of).

538 140 2 140 2 524 5 FIG.B Referring to step S-of, the AMF-checks if the TAI of the TA where the terminal device “UE-X” is located is associated with an AOI event subscription of the type “specific UE”. To this end, the AMF-checks its local AMF context information if that TAI has been indicated in an AOI event subscription message in a “specific UE” context. In the presently considered scenario, this is the case (see step S-).

538 140 2 536 140 2 140 2 140 1 140 2 140 1 140 2 512 5 FIG.B 5 5 FIGS.A andB Still referring to step S-of, the AMF-also checks the subscriber data received in step S-to determine if the AOI event subscription control information (“AOI event applicability” in) indicates the AMF-in association with the TAI of the TA in which the terminal device “UE-X” is served by the AMF-. In the present case, the AOI event subscription control information will indicate for each of the AMF-and the AMF-the TAIs of the AOI of interest that are associated with the respective AMF-and-(as explained above with reference to step S-).

538 140 2 If both conditions are met, then it is determined in step S-that the AOI event subscription applies for the terminal device “UE-X”, and the AMF-proceeds accordingly by triggering AOI event monitoring (e.g., via an EeSubscription indication as generally known).

140 2 140 2 120 110 540 542 110 110 140 2 110 5 FIG.B In the present case, the AMF-thus determines that the terminal device “UE-X” is located in the AOI (status “AOI IN”). As a result, the AMF-sends an AOI event notification (here: an Namf_EventExposure_Notify request) indicative of “AOI IN” for terminal device “UE-X” to the NEF, which forwards this information in an Nnef_EventExposure_Notify request to the AF(see steps S-and S-in). Based on this information, the AFmay start supplying location-based services to the terminal device “UE-X”. The AFmay stop providing the location-based services in response to an AOI event notification indicating “AOI OUT” when the AMF-has determined that the terminal device “UE-X” has left the AOI that is of interest to the AF.

1 FIG.B 150 140 140 150 140 538 150 140 150 170 As has become apparent from the above description of exemplary embodiments, the technique presented herein overcomes one or more of the drawbacks discussed above with reference to. In particular, AOI event subscriptions can also be realized for terminal devicesthat are presently not served by a particular AMFin a particular sub-area of an AOI of interest. Only a single AOI event subscription message is needed per AMF, rather than having to manage a subscription per terminal device. It is the AMFthat locally takes control (see step S-) of whether and when an AOI event subscription shall apply to a particular terminal device. This AMF-based control can optionally be realized via a new subscription type that applies to specific terminal devices (“specific UE”) only. The AMFobtains knowledge for which specific terminal devicesthe AOI subscription shall apply based on extended subscriber information received in the context of registration to the UDM.

170 170 170 170 536 140 1 1 FIGS.A andB 4 5 FIGS.A toB In some variants, the UDMmay be involved in authorizing AOI event subscriptions on per a terminal-basis. Such an approach is not possible in the scenarios discussed above with reference to, as the UDMis not involved in the related signalling. In the procedures discussed above with reference to, the UDMmay, for example, selectively authorize an AOI event subscription (e.g., based on certain criteria defined by one or both of the MNO and individual subscribers). If an AOI event subscription is not authorized, the UDMmay refrain from transmitting the AOI event subscription control information in step S-. As a result, the AMFwill not monitor the event (and evidently, not send a related notification).